1. FIELD OF THE INVENTION
The present invention relates to intensifying screens wherein at least one of the fluorescent and protective layers is colored, whereby the photographic image quality, particularly sharpness, is improved.
2. DESCRIPTION OF THE PRIOR ART
As is well known, the intensifying screen is in face contact with an X-ray film to improve the speed in a photographic system in various fields including radiography for medical purposes such as X-ray radiography used for medical diagnosis or radiography for industrial purposes such as non-destructive inspection of materials. Basically, the intensifying screen comprises a support such as a paper or plastic sheet, and a fluorescent layer formed on one side of the support.
The fluorescent layer is usually composed of a binder resin and a phosphor which is capable of emitting a near-ultraviolet, blue or green color of high luminance when stimulated by radiation. And the surface of the fluorescent layer (the surface opposite to the support) is usually protected by a transparent protective layer such as a polyethylene terephthalate film, a cellulose acetate film or a polymethacrylate film to prevent the abrasion or scratching of the phosphor layer.
It is important for an intensifying screen not only to have a high speed but also is capable of providing a good photographic image quality. For the improvement of the photographic image quality, particularly the sharpness, of the intensifying screen, various methods have been studied including a method in which phosphor particles in the fluorescent layer are arranged with a certain specificity with respect to the particle sizes (U.S. Pat. No. 4,039,840), and a method in which the fluorescent layer is colored (Japanese Unexamined Patent Publication No. 70787/1979).